1. Field of the Invention
The present invention relates generally to railroad switch machinery and, particularly, to a point detector sleeve for a railroad switch machine.
2. Description of the Related Art
Numerous types of known railroad switch machines are used for switching trains between a first set of railroad tracks and a second set of railroad tracks. Switch machines typically are operatively connected with a pair of movable tracks that are connected with one another and are selectably movable and engageable with a first substantially stationary stock rail and a second substantially stationary stock rail. As is generally understood in the relevant art, when one of the movable tracks is engaged with the first stock rail, a train traveling over the tracks controlled by the switch machine remains on the first set of railroad tracks. When the other movable track is engaged with the second stock rail, a train traveling over the tracks controlled by the switch machine is switched onto the second set of railroad tracks.
Most, if not all, railroad switch machines in use in the United States include a power apparatus, a locking apparatus, and a detection apparatus, all of which extend between the switch machine and the movable tracks. The power apparatus provides the motile force needed to move the movable tracks between a first position engaged with the first stock rail and a second position engaged with the second stock rail. The locking apparatus retains the movable tracks in either the first position or the second position. The detection apparatus detects the position of the movable tracks with respect to the first and second stock rails to determine whether or not the movable tracks are correctly positioned and are in a condition whereby a train can traverse the tracks controlled by the switch machine.
The detection apparatus typically includes a point detector bar that extends between the movable tracks and the switch machine. The point detector bar includes a beveled surface that provides a transition between a connector bar portion that is connected with the movable tracks and a shank portion that is opposite the movable tracks, the connector bar having a greater cross-sectional diameter than the shank. The shank includes an externally threaded region upon which a point detector sleeve is threadably mounted. The point detector sleeve has its own beveled surface formed thereon and that is spaced from the beveled surface of the point detector bar.
The detection apparatus further includes a pair of cam followers that are each movably operated by separate linkage systems, and the cam followers are each operatively connected with an indication system. During operation of the detection apparatus, one of the linkages seeks to translate its associated the cam follower from a first position at a first radial distance from the shank toward a second position that is at a second closer radial distance from the shank. Such movement of the cam follower occurs between the two aforementioned beveled surfaces, and at the second radial distance the cam follower is disposed closely adjacent the shank but not in contact therewith. If, however, the movable track associated with the cam follower does not become engaged or is spaced too far away from its corresponding stock rail, the point detector bar does not translate to its anticipated position, with the result that the aforementioned translation of the cam follower will cause the cam follower to engage one of the connector bar and the point detector sleeve. Such a condition causes the indication system to provides an indication that the tracks are unsafe and that trains should not pass over the switch.
As is understood in the relevant art, the beveled surfaces of the detection apparatus are adjusted to correspond with the engagement of the movable tracks with the first and second stock rails. More specifically, when one of the movable tracks is engaged with one of the stock rails, structures connecting the point detector bar with the movable tracks are adjusted until the beveled surface on the point detector bar is only slightly spaced from the associated cam follower. Similarly, the point detector sleeve is rotatably and threadably adjusted on the externally threaded region of the point detector bar such that when the other of the movable rails is engaged with the other stock rail the beveled surface on the point detector sleeve is only slightly spaced from the other cam follower. Such threaded adjustability of the detection apparatus is desirable for a number of reasons related to wear of the components of the switch machine and the tracks, thermal expansion and contraction of components, as well as other factors.
A previously known point detector sleeve 2 is indicated generally in FIG. 1. The previously known point detector sleeve 2 can be generally stated as including a slide tube 4 and a nut 6 that is fixedly attached to the slide tube 4 with a weld 8. As can be seen in FIG. 1, the slide tube 4 is a generally hollow cylindrical member having an inner slide surface 10 that is smooth and free of threads and having a substantially frusto-conic beveled surface 13 opposite the nut 6. The nut 6 includes a threaded nut surface 12 that is threadably cooperable with the externally threaded region of the point detector bar. Such previously known point detector sleeves 2 have not, however, been without limitation.
It is understood that such previously known point detector sleeves 2 have been designed to translate longitudinally in conjunction with the point detector bar according to the movements of the movable tracks. It is also known that railroad tracks and switches provide a highly punishing environment in which components are subjected to substantial impact and vibration loading. In this regard, it has been found that the nut 6 sometimes separates from the slide tube 4 due to a failure of the weld 8. Such failures of the previously known point detector sleeves 2 have resulted in inaccurate indications of the positions of the movable tracks and have required repair of the switch machines in which such failed point detector sleeves 2 have been installed. It thus is desired to provide an improved point detector sleeve that substantially reduces or eliminates the potential for separation of the component having the beveled surface 13 formed thereon from the portion having the threaded nut surface 12.
It is also desired to provide such an improved point detector sleeve in an economical fashion. In this regard, it is understood that in drilling or otherwise cutting a cylindrical hole into a solid bar of material, the drill bit or other rotary cutting tool has a tendency to radially xe2x80x9cwalkxe2x80x9d during the drilling process such that the resulting hole is far from being substantially cylindrical. As such, additional cutting steps such as spiral reaming and the like must be performed on the non-cylindrical hole to make the hole cylindrical. Still additional cutting steps must be performed to ensure that the cylindrical hole is oriented coaxially with a cylindrical outer surface of the block of material. As such, while it would be preferred for an improved point detector sleeve to be formed out of a single piece of material, any method by which such an improved point detector sleeve is manufactured would preferably overcome the shortcomings associated with the multiple process steps otherwise required to form a cylindrical hole that is coaxially oriented with a cylindrical outer surface of a piece of material.
In view of the foregoing, an improved point detector sleeve includes a tube portion and an adjustment portion that are integrally formed with one another as a monolithic member, whereby the point detector sleeve is substantially free of joints between the tube portion and the adjustment portion. The tube portion includes a beveled surface formed thereon, and the adjustment portion includes an internally threaded region formed thereon. In accordance with one method of manufacturing the improved point detector sleeve, a first end of a hollow cylindrical pipe formed with a cylindrical cavity is cut with a rotary cutting tool to form a substantially cylindrical inner surface. The rotary cutting tool advantageously closely follows the cavity to form the cylindrical inner surface without the rotary cutting tool radially xe2x80x9cwalkingxe2x80x9d away from a central longitudinal axis of the pipe. In the first embodiment, the pipe initially has a thicker wall than the wall of the previously known point detector sleeve. In a second embodiment, the pipe is a forged or cast member. In a third embodiment, the pipe has the same wall thickness as in the previously known point detector sleeve, but one end of the pipe is formed with an internally threaded region that receives therein an insert having an externally threaded region and an internally threaded surface.
Accordingly, an aspect of the present invention is to provide an improved point detector sleeve having a tube portion and an adjustment portion that are integrally formed with one another as a monolithic member.
Another aspect of the present invention is to provide an improved point detector sleeve having a tube portion and an adjustment portion and that is substantially free of joints between the tube portion and the adjustment portion.
Another aspect of the present invention is to provide a method of manufacturing an improved point detector sleeve that is substantially free of joints between a tube portion and an adjustment portion thereof in an economical fashion.
Another aspect of the present invention is to provide a method of manufacturing an improved point detector sleeve whereby a hollow substantially cylindrical pipe having a substantially cylindrical cavity is provided, and whereby during a cutting operation a rotary cutting tool closely follows the cavity to provide a substantially cylindrical inner surface.
Another aspect of the present invention is to provide an improved point detector sleeve that is substantially immune to breakage due to a failure of a weld.
Accordingly, and aspect of the present invention is to provide a point detector sleeve for use in a railroad switch machine, in which the general nature of the point detector sleeve can be stated as including a tube portion having a beveled surface disposed at an end thereof, the beveled surface being structured to engageable with a cam follower, an adjustment portion connected with the tube portion and disposed opposite the beveled surface, the tube portion and the adjustment portion being integrally formed with one another as a monolithic member, whereby the point detector sleeve is substantially free of joints between the tube portion and the adjustment portion, the adjustment portion including an internally threaded region, and at least a first tool engagement surface being disposed on the point detector sleeve.
Another aspect of the present invention is to provide a method of forming a point detector sleeve for use in a railroad switch machine, in which the general nature of the method can be generally stated as including the steps of providing an elongated pipe having a substantially cylindrical outer surface and being formed with a substantially cylindrical primary cavity, the primary cavity being coaxially aligned with the outer surface, performing a cutting operation on the primary cavity from a first end of the pipe with a rotary cutting tool to form a substantially cylindrical inner surface that is coaxially aligned with the outer surface and that defines a tube portion of the pipe, forming an internally threaded region on the pipe to define an adjustment portion of the pipe, the internally threaded region being coaxially aligned with the outer surface and being structured to cooperate threadably with a point detector bar, providing at least a first tool engagement surface on the pipe, and forming a beveled surface on the tube portion at the first end.
Another aspect of the present invention is to provide a method of forming a point detector sleeve for use in a railroad switch machine, in which the general nature of the method can be stated as including the steps of providing an elongated pipe having a substantially cylindrical outer surface and being formed with a substantially cylindrical primary cavity, the primary cavity being coaxially aligned with the outer surface, forming a beveled surface at a first end of the pipe, forming an internally threaded region at a second end of the pipe, the internally threaded region being coaxially aligned with the outer surface of the pipe, and providing at least a first tool engagement surface on the pipe.
Another aspect of the present invention is to provide a switch machine, the general nature of which can be stated as including a power apparatus, a locking apparatus, and a detection apparatus, the detection apparatus including a point detector sleeve, a point detector bar having an externally threaded region, a cam follower, and an indication system, the point detector sleeve including a tube portion, an adjustment portion, and at least a first tool engagement surface, the tube portion including a beveled surface disposed at an end of the tube portion, the beveled surface being engageable with the cam follower, the adjustment portion being connected with the tube portion and disposed opposite the beveled surface, the tube portion and the adjustment portion being integrally formed with one another as a monolithic member, whereby the point detector sleeve is substantially free of joints between the tube portion and the adjustment portion, the adjustment portion including an internally threaded region, and the least first tool engagement surface being disposed on the point detector sleeve.